It is often advantageous in mechanical operations to have knowledge of the exact angular position of a piece of rotatable equipment. In those operations in which the rotatable member is unaccessable or otherwise hidden from view, some form of remote reading indication must be provided.
One such operation is the testing of the steam generator tubes in a nuclear steam generator. These tubes are installed in the shape of an inverted U and are tested during maintenance service by inserting an eddy current probe into one lower leg of the U and pushing the probe through the length of the steam generator tube. During that portion of the testing scan in which the probe is traversing the horizontal section of the U, an indication of the relative angular position of the probe with respect to the horizontal plane is required. In this way the exact position of a detected defect may be ascertained.
To accomplish this end, the remote position indicating apparatus employed must be small, simple, and employ an electrical means for communicating between the sensor mounted on the test probe and the test equipment operator outside of the steam generator.